This invention relates to semiconductor devices and integrated circuits, and in particular to providing devices and circuits which can withstand radiation.
Semiconductor devices and integrated circuits generally provide fast and reliable operation in a wide variety of applications. However, if charge is generated in the oxide over the semiconductor, then charges may collect at the underlying semiconductor surface causing inversion and threshold reduction. Since charge generation in the oxide produces a threshold change which, to a first order, is proportional to the square of the oxide thickness, the portion of the device below the field oxide is especially susceptible to this problem.
Charge generation in the oxide can occur due to radiation of various types. For example, gamma radiation from outer space operation or from nuclear explosions can cause this effect. Further, certain processes used in the fabrication of the devices, such as reactive ion etching, can produce radiation which causes charge generation in the oxide.
It is, therefore, an object of the invention to provide a semiconductor device structure which is not susceptible to the adverse effects of radiation charge buildup. It is a further object of the invention to provide such a structure with a minimum of additional processing steps over standard processing techniques.